This invention relates to hot water feeding devices and, in particular, to such devices including an upper tank and a lower tank.
There is a known hot water feeding device which includes an upper tank connected with a water feeding pipe and a lower tank being connected with the upper tank by a conduit and having heater means and a hot water port.
The device of this type is superior to a device including a single water tank because hot water of a predetermined temperature, such as bailed water, can be readily and reliably obtained.
In the device of the two tank type, the conduit for connecting between the upper and lower tanks is so designated that the water heated in the lower water is sufficiently cycled into the upper tank therethrough without a temperature of the water in the upper tank being higher than that in the lower tank.
The conduit serves for not only feeding the water from the upper tank to the lower tank but also permitting air or steam to flow therethrough.
In case the lower tank is not filled to a certain level, the steam in the lower tank is rapidly cooled when water is supplied through the conduit, so that the inner pressure of the lower tank is lowered. Thus the lower tank is subjected to deformation because water flows through the conduit from the upper tank and prevents the air from flowing into the lower tank.
Furthermore, when water is fed to the upper and lower tanks before the device is operated, the lower tank is sometimes not filled with water because the air in the lower tank is not so sufficiently exhausted through the conduit by the disturbance of water flowing down therethrough. In this instance the device is subjected to destruction by following water heating.
The hot water feeding device is sometimes used in automatic selling machines or vending machines, such as coffee or other goods selling machines. In that case, required amount of hot water is different in each good. Accordingly, it is desired that different amounts of hot water are fed during a constant time period.